I. Field of the Invention
The present invention relates to compositions and methods for treating metal surfaces to increase their resistance to corrosion. In a specific embodiment, the invention relates to compositions and methods for treating downhole metal surfaces present in oil and gas wells to inhibit corrosion thereof.
II. Background of the Invention
Corrosion of metal surfaces due to reactions between the metal and its environment is a problem that is well known. If not properly controlled, corrosion can lead to great financial loss and wastage of materials.
Metal surfaces present in oil and gas wells are particularly susceptible to corrosion. Oil and gas wells typically contain water that has a high electrolyte concentration as well as many highly corrosive chemicals such as hydrogen sulfide, carbon dioxide and various organic acids. Corrosion of metal surfaces is particularly a problem in deep-sea oil and gas wells where temperatures of 90.degree. C. or higher and pressures of 1000 psig or higher exist. The extreme conditions of pressure and temperature act to increase the rate of corrosion and make the problem more difficult to deal with.
Excessive corrosion of pipes, pumps and other equipment that are present in or used in association with oil and gas wells is a serious problem that, if not sufficiently controlled, can lead to premature failure of the equipment resulting in high maintenance and parts replacement costs. As a result, it is necessary to treat the metal surfaces of pipes and other equipment present in or used in association with oil and gas wells to prevent or at least inhibit corrosion thereof.
A variety of corrosion-inhibiting agents and techniques for treating metal surfaces have been developed heretofore. Many of the corrosion-inhibiting agents developed heretofore are not stable under the conditions typically encountered in oil and gas wells and inhibit corrosion of metal surfaces present in or associated with oil and gas wells for only a short period of time, if at all. It is too expensive and inconvenient to reapply a corrosion-inhibiting agent on a frequent basis, particularly if the well is not easily accessible and/or if, as in the case of offshore wells, the well is difficult to treat. Due to their high molecular weight and low solubility, many conventional corrosion-inhibiting agents tend to gunk up in oil and gas wells which results in other problems. Some conventional corrosion-inhibiting agents are not compatible with other well treating agents and cause more corrosion than they reduce.
By the present invention, an improved corrosion-inhibiting composition and method of treating a metal surface with the same are provided. The corrosion-inhibiting composition and method very effectively prevent or at least inhibit corrosion of metal surfaces present in or associated with highly corrosive environments such as environments typically encountered in oil and gas wells.